1. Field of the Invention
The present invention relates to a routing machine which is especially useful for facilitating fabrication of commercial signs of the type having letters or logo symbols cut out of or into a sheet of material such as metal, or in the alternative for cutting the letters or symbols themselves as separate entities for attachment to a support. The machine has a controllable arm which is shiftable in a manner to move a cutting bit along a path determined by a directly related template-engageable guide pin associated with the bit.
2. Description of the Prior Art
Signs having raised or recessed three-dimensional letters, or of a nature where the letters or symbols are flush mounted but of a different material than the main body of a sign are both readily perceptible and aesthetically pleasing. Such signs are typically manufactured from wood, wood products, plastic, or metal such as aluminum and, like their flat, painted counterparts, are usually produced on an individual, custom made basis. Unfortunately, the milling or routing machines commonly used to date to cut the letters either out of a sheet which is then backed up with a translucent panel or individual letters from flat stock, are not only inefficient but also present certain hazards to the worker's hands.
Best results are obtained when free-hand cutting is avoided and the router caused to follow a template which guides movement of the cutting bit. Signs or letters and symbols have in the past been milled by an inverted table router which has an overhead, downwardly directed, cylindrical guide pin coaxial with and spaced at a slight distance from an opposed, upwardly extending, coaxially aligned cutting bit. The template is secured to the upper surface of the workpiece, and as the periphery of the template is moved along the stationary guide pin, the underlying bit simultaneously cuts the workpiece.
Use of an inverted table router, however, is generally unsatisfactory for cutting multiple letters or symbols from a large sheet of material, as each template must be fastened with nails or glue to the workpiece itself, a disadvantage in many instances and inconvenient at best. Also, wood chips or other debris thrown from the cutting bit may wedge temporarily between the adjacent guide pin and the template whereupon the router is subsequently thrown off course. Also, it is possible for the cutting bit to accidentally gouge the proximal template such that a new template must then be painstakingly fashioned.
Operators using inverted table routers also suffer a noteworthly disadvantage from the lack of ability to see the quality of the cut, such that once the operation is completed, the template and workpiece must be removed from the support table and turned over to inspect the smoothness of the finished edge. It is also important to note that if the router bit was instead disposed over the table and the guide pin was mounted to extend upwardly from the table toward the bit, then although the finished edge could be seen the user's vision of the template would be obstructed, for the most part, by the workpiece itself, such that the user would be unaware of deviations of the template edge from the guide pin. Consequently, whenever the template and workpiece are sandwiched together, the vision of one or the other during the cutting operation must, by necessity, be substantially blocked.
Another method of milling sign cutouts or letters and symbols which has been proposed in the past is the use of a router mounted on a device similar to a pantograph. However, the multiplicity of arms and joints are subject to binding and considerable free play such that a less than desirable finished result is usually obtained.
Microprocessor controlled routers have recently been introduced into the market but they are prohibitively expensive and are difficult if not impossible to pre-program for all types of symbols and letters to be formed, noting in this respect that many if not all signs have individual art work letters, but even if somewhat standardized in form, are necessarily of different sizes from sign to sign.